Various means have been used in the prior art to safe and arm a missile and to prevent the missile from being prematurely, or inadvertently detonated by an extraneous signal. Frequently it is necessary to assume with a minimum of uncertainty that all the conditions of a normal flight are satisfied before the final arming sequence is accomplished. Usually safing and arming signatures are monitored by on board sensors and processed by logic circuits before the arming sequence is finally initiated. After all conditions are satisfied within the acceptable limit of uncertainty, it is necessary to transmit intelligence signals across a physical isolated zone to the warhead critical circuits. Previous methods in some instances utilized dual signal paths and/or coded signals, usually electrical in nature to transmit the intelligence across the isolation distance. One of the problems with prior art devices utilizing coded electro-magnetic radiations to activate the critical circuit has been their susceptibility to being jammed or fired by electronic or nuclear countermeasures. In other instances the aforementioned devices have been found to be susceptible to premature firing because of the electrical breakdown of a circuit component due to leakage currents or the shorting of a critical element aggravated by a severe environmental stress condition. The problem with the use of D.C. operated switches or use of standard type stepping motors in missile applications is that they can easily be made to malfunction upon receipt of a random noise or spurious electrical signal which places the missile in a condition of fail-arm rather than fail-safe. Multiphase motors are likewise generally unsuitable for missile switching applications because of their low holding and operating torque and the adverse affects thereon by the high stresses imposed by spin, pitch, yaw and setback forces of the missile. In view of the aforementioned problems the present invention overcomes these problems by making the critical arming function dependent upon input signals via three different transmission media which are not readily subject to change from high stress environments nor electronic countermeasures.